The objective of the peptide structure mass spectrometric analysis section of the Abeta core is to provide support and promote the proposed projects by carrying out structure analysis of amyloid beta-protein (Abeta) using immunoprecipitation/mass spectrometry (IP/MS) and by providing experimental data on chemical modifications of apolipoprotein (apoE and apoJ) using mass spectrometric peptide mapping technique. There are five specific aims: (1) to determine the primary structure changes of Abeta introduced by apoE isoforms of apoJ in cultured cells; (2) to determine the peptide compositions associated to Abeta distribution among apolipoprotein particles; (3) to identify Abeta metabolites generated in vivo; (4) to characterize Abeta profiles in transgenic mice; and (5) to determine the chemical modifications on apolipoprotein resulting from different conditions (e.g. the presence of reactive oxygen species and apoE antisense therapy). Abeta and its variants will be analyzed by IP/MS. In IP/MS Abeta peptides is captured specifically by monoclonal anti-Abeta antibodies and their molecular masses are accurately measured by the state-of-the-art mass spectrometer. The nature of chemical modifications (type and position) on apoE and apoJ will be determined by mass spectrometric analysis of enzymatic digested peptides of these proteins using MS peptide mapping and MS2 experiment. All of these results will be correlated with those from biochemical, cellular and immunocytochemical studies. The detailed structure characterization of Abeta as well as apolipoprotein proposed in this application will greater facilitated the proposed studies and provide essential information to understand the function on beta-amyloidogenesis in Alzheimer's disease.